Cryptology ePrint Archive: BibTeX Citation of Report 2013/190

@misc{cryptoeprint:2013:190,
    author = {Shaohua Tang and Jianhao Wu and Weijian Li and Zheng Gong},
    title = {Power Analysis Attacks against FPGA Implementations of KLEIN},
    howpublished = {Cryptology ePrint Archive, Report 2013/190},
    year = {2013},
    note = {\url{http://eprint.iacr.org/}},
}

You will need the url.sty package (comes with most LaTeX installations) for the last line. Otherwise, remove the \url command.